The invention relates to a sealed turbine generator and to method to repair a hydrogen cooled generator, particularly to seal bushings at a solder seal between a hydrogen atmosphere on one side of a stator frame terminal plate and air on an opposing side of a high voltage turbine generator.
High voltage turbine generator bushings carry power that is developed in stator windings. The windings are encompassed within a hydrogen pressurized stator frame. The bushings penetrate through the stator frame at the frame terminal plate to the outside. The locations where the bushings pass through the plate are sealed to keep hydrogen from leaking out of the frame.
Hydrogen leaks develop between the bushing flange at the frame terminal plate and the frame wall or at solder seals between the bushing flange and the bushing porcelain wall. The hydrogen leaks create hazardous conditions that can result in explosion on either the outside or the inside of the generator.
Hydrogen leaks require generator shut down for repair. Preferably, the leaks are repaired without bushing replacement. If bushing replacement is required, desirably the leak is temporarily repaired to “buy time” to obtain replacement bushings. The temporary repair should take only a few days to minimize “down time.” One temporary repair involves taking the generator off line, degassing the stator frame and sealing the leak with a temporary sealing composition to provide time to plan a major shut down when the bushings can be replaced. In one temporary repair procedure, the annulus seal on the hydrogen side of the bushing penetration is cleaned and layers of sealing materials are applied to the leak area. This procedure effectively seals leaks between the bushing flange and the generator frame. However, this repair is not effective to seal leaks between the bushing flange and the porcelain at the solder seal.
There is a need for a sealed generator and method to seal a spacing between a terminal plate and particularly, there is a need for a sealed generator and method that will effectively seal leaks between the bushing flange and the solder seal of bushing penetrations of a stator frame at the frame terminal plate.